1 Land contracts or contracts for deed are a security agreement between a seller, called a Vendor, and a buyer, called a Vendee.  The Vendor agrees to sell a property by financing the purchase for the Vendee.
The two DNA strands are held together by interchain hydrogen bonds. H-bonds pair the bases in one chain to the complementary bases in the other chain. (A/T and G/C).
DNA helicase unzip, or separate, a strand of DNA at positions called origins. This means that the hydrogen bonds between complementary base pairs are removed (DNA is double stranded!). When they separate double-stranded DNA into single strands, it allows each strand to be copied (replication).